In the production of data storage devices such as magnetic disc drives, production cost and performance must be constantly balanced and many design tradeoffs must be made. One such tradeoff in disc drives relates to the size of the servo power device for the voice coil motor (VCM) and the spindle motor. VCM moves the actuator over the discs in the disc drive while spindle motor is spinning. Smaller servo power device dies are less expensive and, thus, lower production cost. However, smaller die size may result in high resistance, which in turn increases the internal device temperature at a given running current for desired performance requirement, such as, access time and spindle speed, etc.
A power device internal temperature can severely affect the drive's performance. The power device can overheat causing drive operation error, such as seeking error, track following error, etc. To protect the power device from causing damage to itself by operating at too high a temperature, most power devices monitor the internal temperature and are designed to go into thermal shutdown if the temperature gets too high. A thermal shutdown is triggered by hardware when the internal temperature reaches a pre-defined threshold. In addition, temperature sensitivity is exacerbated when the ambient environment temperature is already very high as is now common in modern computers and electronics. When a thermal shutdown occurs, the VCM retracts the actuator. This will normally be followed by a spin down and spin up retry and will result in a severe error and dramatic performance drop.
Hardware means for reducing power dissipation may be used in the drive. However, these increase cost. Other methods for reducing power dissipation include introducing time delays between seeks, but these methods decrease drive performance.
Accordingly there is a need for an inexpensive method to reduce the power dissipation from a VCM. The present invention provides a solution to this and other problems, and offers other advantages over the prior art.